I'm not mechanically inclined, and I live in a very rural area so I'm kind of at the mercy of these little repair places. I'm going to try to ignore it but its hard to when I'm sitting at a light with my heat or headlights on and the gauge drops and you can kind of feel it in the way the truck idles.

 

I think you just didnt notice the gauge fluctuation prior because it wasnt on your mind! Happens all the time... people nnotice small little noises they never heard before because they had a blowout and are now paranoid.etc

Your 2nd battery. You prob had a blem.
Fluctuation is normal. Maybe it does fluctuate more than it used to because the afermarket alternator may not create as much power at idle as your OEM did. Not all alt's can be treated the same.

When a resistor blows, it creates an open circuit. This means it can no longer RESIST the current and the current flows steadily, hence why you can only have HIGH blower fan.
"shorting out" is ridiculous sounding and is not the case. Mechanic has no idea how electronics work if he is saying such a thing. You can certainly drive indefinitely with a bad blower resistor!!

What I would do that I heard nothing about, is verify your ground cables are solid. You can use a multimeter in the Ohm setting and check the resistances of the cables. The reading should not be greater than 1 Ohm or it has excessive corrosion inside. You should be getting 0.X Ohm type of readings. All you do is put a probe on each end of the wire being tested. You do not have to unhook anything.


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2008 Dodge Ram

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Ok thank you for your help. Yes I agree I am probably more aware of it now and a bit fixated on it. It was the dodge dealership that made me so upset and paranoid. I was 800 miles from home when they told me don't drive home using the heat with the bad resistor because I would fry everything. So yes now I'm paranoid and probably a little fixated on that gauge now. It's been frustrated because I'm getting so much mixed info from different mechanics here where i live so I didn't know what route to go.

 

The truck has 164,000 miles on it and the serpentine belt was worn, so I don't regret replacing that it needed it anyways with that amount of miles on it, but I probably just pissed away $300 on an unneeded alternator lol. Oh well live and learn.

 

After the dealership told me that I was afraid I had ruined the truck electrical wise. Iv had Fords, and Chevys, and I must say this dodge ram beats them all I love it, it's without a doubt my favorite truck iv ever had. With all those mile it drives awesome and leaks not a drop of anything. I travel between tennessee and Florida a lot to see my kids so it gets a lot of use and interstate miles, and has held up like a champ.

 

You have a 2008, which ha s a TIPM(Totally Integrated Powertrain Module)
It's a fancy and expensive circuit board that replaces the old mechanic relays. IF it senses a circuit drawing too much current it shuts that circuit down..permanantly(causing you to buy a new one). So, there's no way your going to 'fry' your truck....

After completing my degree in Electronics Engineering, I realized how little the majority of the mechanics actually know about circuitry and rely heavily upon the scan tools to do the work they should really know. With all of the onboard electronics, they should have to take aditional schooling for the amount car owners pay for service work and their misdiagnosis!

 

Yes I agree because it was the dodge dealership that told me I would fry my powertrain module. I drove most of the way from Florida to tennessee with my kids scared to use the heat because of what they told me we about frikken froze to death until the last 2 hours I finally couldn't take it any longer and used the heat on the high setting. And after being told so many different things from different mechanics here where I live I was so confused i didn't know what to do,

 

Thanks for the info it was nice to get some straight up answers about this from someone for a change.

 

No prob

 

Ok someone help please. 08 ram 4.7 v8 lone star. My problem has not changed. Had a new batery, alternator,and serp belt put on. The volt. Gauge goes below half when I'm stopped at a light only when my lights are on. If I sit long enough itl idle up a little and the gauge will go back to a little above half or if I put it in park itl go back up. Also when the lights are on I can hear a slight whistle and itl stop when I turn the head lights off. No one can figure out why it's doing this.